DIRECT LARYNGOSCOPY KILLED THE VIDEO STAR?

Videolarygoscopy (VL). Brave new world. VL makes any intubation easy, and solves airway managment problems. Well, it can be a life-saver, but it also brings its own set of problems. Two new RCTs comparing VL and DL are just out. One study looks at using VL as the primary intubation tool in the pre-hospital setting, and next to the old laryngoscope it pales in comparison. Bit there might be more to the story. Let’s have a look.

Setting
When I started out in anaesthesia, fibre-optic intubation (FOI) was the gold standard for difficult airways. Videolaryngoscopes largely killed of FOI. VL could do difficult intubations and even awake intubations. A few settings remain for FOI, but they mostly hang in their expensive racks these days. Everyone was excited about VL, and some predicted it would take over laryngoscopy and airway management entirely, laughing at the old-timers with the old laryngoscopes. But not so fast…

Study
The Glidescope Ranger is a more portable version of the well-known Glidescope, and this study wanted to see if it was a reliable alternative to the old laryngoscope. They randomised pre-hospital intubations to the Ranger or standard direct laryngoscopy in four Austrian and Norwegian physician manned HEMS. These are manned with anaesthetists and emergency docs, well capable of intubation, and airway management strictly followed a prehospital algorithm. For thsi study, the first and second intubation attempt used GlideScope or direct laryngoscopy as randomized; third attempt crossover. After three failed intubation attempts, immediate use of an extraglottic airway device.

Results
They got around 160 patients in each arm. Successful intubation with the Glidescope was 62% and with the old laryngoscope 96,2%. Ouch. Reasons for failed videolaryngoscopic intubation:

Failing to advance tube into larynx or trachea (26/168)
Impaired sight due to blood or fluids (21/168)

For failed VL, DL was successful in 61 of 64 patients (95.3%), but reversely when DL failed, VL succeeded only in 4 of 6 cases (66%). In addition, VL was prone to impaired visualisation of the monitor due to ambient light (29/168).

Discussion
Hmmm… What to make of this. I think the problem of advancing the tube can be real, but mostly mitigated by training. These numbers might just show that these pre-hosp docs have more experience and are more comfortable with the old laryngoscope. The blood and fluid problem is real, and can especially be a problem in the emergency and pre-hospital setting. Also, monitor impaired by sunlight is a problem you’d only encounter pre-hospitally. It can actually also be a problem with DL, if the sunlight is Australia-strength.

So, VL should probably reach into 80%-something with more training, but still a long way from direct laryngoscopy’s 96.2%. And intubation success should really be high in the 90’s.

Just to put it in perspective, intubation success of 90% means 1 in 10 has a failed intubation. Even a 95% success means 1 in 20 has a failed intubation. That’s not acceptable. It should really reach close to 98%, where it’s only 1 in 50 that have a failed intubation by the first and preferred method. So even direct laryngoscopy could improve a little here – but VL isn’t even close. Failed intubation for 1 in 3 patients is not acceptable.

But we love VL as a back-up tool, still, here it only rescued 2 out of three airways? I think the study design forced the docs to give VL a chance even when the found it relatively contraindicated (ie soiled airway). In other settings, and with proper VL technique, I find VL is a great bakc-up tool. Also, the study shows VL won’t do as the primary and only intubation tool in all settings. DL is still superior in a messy airway.

The VL strikes back
There are several studies suggesting that VL is as good, or better, at getting first pass success for intubation. Another study, randomising ED intubations to VL or DL shows a different story. About 100 patients in each arm. VL gets a first-pass success of 92%, but DL only gets 86%. Those numbers look similar, but they mean that 1 in 12 gets a failed first-pass with VL and 1 in 7 gets a failed first-pass with DL. That makes the difference seem bigger. The failed intubations are also the interesting numbers, because only very small numbers are acceptable, and even small fluctuations means big differences in NNH.

Take note that these two studies measure different things: the first one gets two attempts at intubation, the second one only looks at first-pass success. So the numbers aren’t comparable. However, first-pass success should be up in the high(ish) 90s for direct laryngoscopy for highly trained intubators. So in this last study, the training and experience with VL and DL seem flipped compared to the first study.

Still, direct laryngoscopy performing so well in the difficult prehospital setting where videolaryngoscopy clearly has some disadvantages, is something to ponder.

Conclusion
There is no perfect weapon for intubation. Also, the tool is only as good as the operator. What I take from these studies is that I need to keep myself trained in both DL and VL, and choose the right tool for the job at hand. This means that the old laryngoscope will usually be my first choice, but the videolaryngoscope is a vital back-up tool.

5 Responses to DIRECT LARYNGOSCOPY KILLED THE VIDEO STAR?

The problem is the increased angle/curvature of most VL-devices (including the glidescope) which, while providing an excellent view of the glottis, means that the tube hits the larynx angled anteriorly, hitting the anterior wall of the larynx and making it hard to pass it down the trachea. The fact that the extreme curve also makes it necessary to use a stylet makes the tube even harder to “bend down into the trachea”. Both my former and current hospital has the CMAC, the former had the regular curve Mac blades, while my current only has the hyperangulated dBlade – and it is much more difficult to pass the tube. It is a bit easier with a bougie, but still requires a bit of manipulation and rotation to be able to pass it down the trachea.

I don’t quite understand the need for such an extreme angle, in 3 years using the regular curve mac blade I only ever had to switch to the hyperangulated blade once. Seems like the benefit of the extra angle on the visualization of the glottis is pretty much lost in the added difficulty of actually passing the tube, something this study also suggests…

I totally agree. Like all new tools, there are new techniques and tricks to learn, and passing the tube when using a hyperangulated blade will be somewhat easier with training. So, I think these studies also reflect the specific doctor group’s training with each device. Thanks for your comment.

Interesting studies! The Glidescope is a different technique. And thus.. for prehospital providers like paramedics diffucult to learn. The C-Mac is also a slightly different technique. With The McGrath however, prehospital providers can keep using their classic technique with an extra tool.
It will help, just as an extra tool, and in my opinion is improving the succesrate. At the moment we (Ambulance/EMS ervices Rotterdam AZRR) are performing the VIPS Study: comparing first pass an attempt between classic and VL using a McGrath VL by ambulancenurses/paramedics.
We are halfway our 500 inclusions and hope to finish the study at the end of 2017.
I agree any misintubation is not acceptable and a succesrate from 95% is too low if the endpoint is a tube in the trachea. On the other hand I think the focus is too much on ‘a et tube in place’ . I think the focus needs to be a good ventilation and the most safe and acceptable airway in the prehospital field.
I also agree that nothing can replace exposure! But sometimes that is simply not possible and realistic and we need to search for the best way to perform adeqaute and safe airwaymanagement in the prehospital field.

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About ScanCrit

A blog on anaesthesia, intensive care and emergency medicine. In-hospital and outside. Mostly focusing on the critically ill patient. Written by two Scandinavian senior anaesthetic registrars turned consultants.

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